You are looking at the Doepfer A-183-9 Quad USB Supply Module.
The A-183-9 is a simple power supply for up to four devices which can be powered or charged via USB (e.g., keyboards, smartphones).
The module has no USB function but provides only a +5V supply for USB devices.
A control LED shows if the +5V voltage is present.
Note: The module requires an A-100 case with built in power supply A-100PSU3 ! Only this A-100 supply has the required +5V available. We do not recommend the usage of an older A-100 case with A-100PSU2 as this would require the +5V adapter A-100AD5 and the max. current would be limited to 100mA. In particular module A-183-9 cannot be installed into the cases A-100LC1, A-100LC3 or A-100MC because these cases do not have +5V available (A-100LC3) or the current at +5V is very limited (only 50mA for A-100MC or A-100LC1).
Each of the four USB sockets is connected to the +5V supply of the A-100 Bus via a 0.3 Ohm resistor. These resistors work as protection against short circuits. On the other hand, this measure causes a voltage drop that depends upon the current which is taken by the USB device. For example, 1A current causes a 0.3 Ohm * 1A = 0.3V voltage drop so that only 4.7V remain. Some USB devices may then not recognize the USB supply and will not be charged. The only solution is to shorten the protection resistor in question on the A-183-9 board e.g., by means of a solder joint. The resistors are named R1...R4. Pay attention that in this case the short circuit protection gets lost.
Module A-183-9 provides only the signals GND and +5V at the USB sockets. Some devices require additional signals at the USB terminals D+ und D- to start the charging process (especially Apple devices). Such units cannot be charged by the module because of the missing D+ and D- signals.